1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device represented by a thin-film transistor. More particularly, the present invention relates to a method of manufacturing a semiconductor device using a silicon thin film having crystallinity which is formed on a glass substrate or a quartz substrate.
2. Description of the Related Art
Up to now, there have been known thin-film transistors using a silicon film. The thin-film transistor is structured using a silicon film (several hundreds to several thousands .ANG. in thickness) formed on a glass substrate or a quartz substrate.
The reason why the glass substrate or the quartz substrate is used is to employ the thin-film transistor for an active matrix liquid-crystal display unit.
Under existing circumstances, in the case of using the glass substrate, a general technique is that the thin-film transistor is formed using the amorphous silicon film. In the case of using the quartz substrate, a technique in which the crystalline silicon film obtained through a heat treatment is used has been put to practical use.
Compared with the thin-film transistor using the amorphous silicon film, the thin-film transistor using a crystalline silicon film enables high-speed operation of two digits or more to be performed. Hence, a peripheral drive circuit of the active matrix liquid-crystal display unit, which has been conventionally made up of an IC circuit externally attached hereto can be formed of a thin-film transistor on the glass substrate or the quartz substrate.
The above structure is very advantageous in the downsizing of the overall device or simplification of a manufacturing process. Also, the structure leads to reduction of the manufacturing costs.
As a technique by which a crystalline silicon film is obtained through a heating treatment, there has been known a technique disclosed in Japanese Patent Unexamined Publication No. Hei 6-232069. According to the technique, a metal element (for example, nickel) that promotes the crystallization of silicon is introduced into an amorphous silicon film so that the crystalline silicon film is obtained through a heat treatment at a lower temperature than a conventional one.
Using that technique, an inexpensive glass substrate as can be used as a substrate, and the crystalline silicon film as obtained can provide crystallinity which can be practically used over a wide area.
However, because the metal element is contained in the film and the control of its introduced amount is subtle, it is proved that there arise problems on the reproducibility and the stability (electric stability of the obtained device).